BRPI0712768B1 - METHOD FOR ADHERING A MOVIE BY TAKING A FLAT INITIAL FORMAT TO A CURVE FACE OF A SUBSTRATE AND DEVICE TO CARRY OUT THE SAME - Google Patents

Abstract

A method of bonding a film (2) to a curved substrate (1) comprises preforming the film by applying a pneumatic pressure difference between two sides of the film and by heating said film. An intermediate shape is then conferred on the film, which is suitable for applying the film against a curved face of the substrate. This application is carried out, on the one hand, by keeping the film m the intermediate shape by means of an adjusted pressure difference applied between the two sides of the film and, on the other hand, by pressing the substrate against the film by means of a movable support (12-14). Such a method is used to obtain a defect-free ophthalmic lens with a film bonded to it.

Description

(54) Title: METHOD FOR ADHESING A FILM HAVING A FLAT INITIAL FORMAT TO A CURVED FACE OF A SUBSTRATE AND DEVICE TO DO IT (51) Int.CI .: B29C 63/00; B29C 51/10; B29C 51/16; B29D 11/00 (30) Unionist Priority: 13/06/2006 FR 06/05247 (73) Holder (s): ESSILOR INTERNATIONAL - COMPAGNIE GENERALE DOPTIQUE. CENTER NATIONAL DE LA RECHERCHE SCIENTIFIQUE - CNRS (72) Inventor (s): PAUL LEFILLASTRE; ANTOINE MARTY

1/13 "METHOD FOR ADHESING A FILM HAVING A FLAT INITIAL FORMAT TO A CURVED FACE OF A SUBSTRATE AND A DEVICE FOR DOING THE SAME" [0001] The present invention relates to a method for adhering a film to a curved substrate. It also refers to a device designed to implement such a method.

[0002] It is often useful to adhere a film to a curved face of a slow lens or a spectacle lens to obtain a lens that has a desired property. For example, the film can be a polarization film, a contrast-enhancing film, a photochromic film, etc. Since the lens face is curved, it is not possible to apply the film directly to the lens when the film has an initial format that is flat. This is due to the fact that delamination, tearing and / or folds appear due to the difference in curvature between the film and the face of the lens. Therefore, it is necessary to preform the film to give it an appropriate initial curvature before applying it to the lens.

[0003] Normally, the film is pre-formed by thermoforming, by pressing a block on one side of the film so that the face of the film that is located on the same side as the block becomes concave and the other side of the film becomes become convex. The film may have been heated in advance to make it more flexible when it is deformed by the block. However, such pre-forming method generates great tensions in certain parts of the film, essentially in peripheral parts of the latter, which result in local stretching or even tearing of the film. In addition, that face of the film against which the block is pressed is often damaged, due to the rubbing that occurs between that face and the block. It has micro-scratches that can be visible or can cause slight dispersion. Finally, particles and dirt can also be embedded in the film by the block during preforming. [0004] An objective of the present invention, therefore, is to propose a new method for adhering a film to a curved substrate, for which the stresses generated in the film are reduced, and which does not create surface defects in the film.

[0005] For this purpose, the invention proposes a method to adhere a film

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2/13 having a substantially flat initial shape to a curved face of a substrate, the method comprising the following steps:

a) when the film is at a temperature above 40 ° C, a peripheral edge of the film is firmly retained and a pneumatic pressure difference is applied between two sides of the film until a film application face becomes curved with a curvature greater than an average curvature of the substrate face.

b) when the temperature of the film has dropped below 40 ° C, the difference in pneumatic pressure applied between the two sides of the film is adjusted so that the curvature of the film application face becomes approximately equal to or less than the curvature of the substrate face; and

c) while maintaining the pneumatic pressure difference set in step b), the substrate face is pressed against the film application face until a complete contact is established between the film and the substrate face, a layer of an adhesive being placed between the film and the substrate.

[0006] Thanks to the adhesive layer used in step c), a method according to the invention adheres the film to the substrate. The set obtained is then permanent and provides an element that combines the respective properties of the film and the substrate. In this set element, the film is adhered to the curved face of the substrate, with that face of the film called the application face facing towards the substrate. The film can provide the set with an optical property, such as coloring, a polarizing power, photochromic behavior, etc., or surface properties, such as hydrophobic behavior, an anti-dirt effect, protection from scratches, etc.

[0007] According to the invention, the method includes a first step a) of preforming the film, which is carried out by applying a pneumatic pressure difference between the two faces of the film. Such pre-training has at least two advantages. First, the tensions that are generated in the film, to give the

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3/13 even with a curved shape, they are well distributed and therefore not very likely to form localized stretch or tear of the film. Second, the film is held in place by its peripheral edge and the deformation of the film is created by a higher gas pressure that is applied to one side of the film. No solid object, which could have a counterform function, for example, is therefore in contact with the central part of each face of the film during preforming. In this way, there is no scratch on the film, nor is any foreign particle embedded in the film faces.

[0008] Furthermore, thanks to the use of a pneumatic pressure difference to preform the film, the temperature of the latter can be controlled precisely during pre-forming, especially in relation to the glass transition temperature of the film. In this way, the format given to the film before being assembled with the substrate can also be well controlled, while still ensuring that the temperature of the film during step a) remains below a threshold temperature above which the film could be degraded. By controlling the temperature, it is possible, in particular, on the one hand, to extend, where appropriate, the phase during which the film is subjected to plastic flow and, on the other hand, to avoid sudden cooling, which together contribute to minimize, during assembly , residual stresses of thermo-mechanical origin.

[0009] In addition, step c) is carried out using two independent control means: the difference in pneumatic pressure applied between the two sides of the film on the one hand, and a device for pressing the substrate against the film on the other. In this way, the film is held in place by the pressure difference with the format that is given to it in step b) while adhesion is taking place. In this way, no unintended displacement of the film occurs, so that adhesion can be carried out with precise alignment of the film and the substrate that are facing each other.

[0010] A method according to the invention therefore makes it possible to obtain a set, consisting of the substrate and the film, which has very good optical quality. This quality is compatible with many applications of the substrate provided with the film. In

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4/13 In particular, the method is compatible with ophthalmic applications. The substrate can therefore be an optical lens, an ophthalmic lens, a lens for sunglasses, etc. [0011] According to a first way of implementing the invention, which is appropriate when the substrate face is convex, the pneumatic pressure difference is applied between the two sides of the film in step a) so that the application face of the film becomes concave with a greater curvature than the curvature of the substrate face. Then, in step b), the difference in pneumatic pressure is reduced so that the film application face remains concave and the curvature of the latter becomes less than the curvature of the substrate face. Then, in step c), the contact between the film and the substrate face, via the adhesive layer, can be initiated in a central zone of the film and the substrate. The contact zone then grows progressively and radially as the substrate is applied with increasing force against the film until the contact zone corresponds to the entire face of the substrate. In this way, no bubbles are formed between the substrate and the film during adhesion, since adhesion is carried out by expelling air from the center towards the peripheral edge of the film.

[0012] According to a second way of implementing the invention, the difference in pneumatic pressure applied between the two sides of the film in step a) is such that the film application face also becomes concave with a greater curvature than the curvature of the substrate face. Step b) then comprises the following two substeps:

b1) when the temperature of the film has dropped below 40 ° C, the difference in pneumatic pressure applied between the two sides of the film is reduced so that the application face of the film remains concave and the curvature of the application face becomes substantially equal to the curvature of the substrate face; and then b2) the pneumatic pressure difference is modified by reversing the sign of that pressure difference between the two sides of the film so that the application side of the film becomes convex.

[0013] This second method of implementation is appropriate when the face of

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5/13 substrate is convex or concave. In particular, when it is convex, the film application face becomes concave again when the substrate face is progressively pressed against the film application face in step c). In this way, the adhesion of the film to the substrate is initiated again in a central zone, which propagates radially to an increasingly larger zone. In this way, the adhesion obtained is again free of bubbles.

[0014] The invention also relates to a device suitable for implementing an adhesion method, as described above. Such a device comprises:

- a sealed chamber provided with a system for fixing the peripheral edge of the film in order to hermetically seal that chamber with the film;

- a device for heating the film and a device for controlling the temperature of the film, which is fixed in the chamber;

- a device for varying the pneumatic pressure inside the chamber and a device for controlling that pneumatic pressure in relation to the pressure outside the chamber;

- a substrate support placed in the chamber; and

- a device for moving the substrate support within the chamber, which are designed to press the substrate against the film.

[0015] Such a device is particularly advantageous when it makes it possible to carry out steps a) to c) without disassembling or manipulating the film between two of these steps. In this way, any risk of the film being scratched or damaged is reduced. This is because steps a) and b) can be performed by triggering the device to vary and control the pneumatic pressure inside the chamber on the one hand, and the temperature of the film on the other hand, and step c) is performed by triggering the device to move the substrate support.

[0016] Advantageously, the device can additionally include an automatic control system designed to trigger both the device to vary and control the pneumatic pressure inside the chamber, the device to vary and control the temperature of the film, and finally the device to move the film. substrate support.

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Therefore, it is possible to mass produce composite elements consisting of a film attached to a substrate, in a reproducible, inexpensive and high-quality way. [0017] Other advantages and features of the present invention will become evident in the following description of exemplary non-limiting modalities with reference to the attached drawings, in which:

Figure 1 is a sectional view of a substrate that can be used to implement the invention;

Figures 2a-2d are respective sectional views of films that can be adhered to the substrate of Figure 1, according to the invention;

Figure 3 is a sectional view of a device suitable for implementing an adhesion method, according to the invention;

Figures 4a-4d illustrate a first way of implementing the invention; and Figures 5a-5e illustrate a second way of implementing the invention.

[0018] For the purposes of clarity of the figures, the dimensions of the elements shown are not in proportion to effective dimensions or ratios of effective dimensions. In addition, identical references in the various figures indicate identical elements, while N indicates a fixed direction that is repeated in several figures.

[0019] As shown in figure 1, a substrate 1 consists of an ophthalmic lens. This lens can be a model of spectacle lens, that is to say a lens that has not yet been cut to the dimensions of a frame for the purpose of being fitted into it. Lens 1 can consist of any material commonly used in the ophthalmic field, whether it is a mineral material, an organic material or possibly a composite material. It can be a correction or non-correction lens, for example, of the unifocal, bifocal, trifocal or progressive type. This lens can be optionally tinted by volume. It will be understood that the invention is independent of the type of lens used. S1 indicates the convex face of lens 1, or the rear face with reference to the position of the lens when used by a person wearing glasses.

[0020] It will be remembered that two curvatures are defined at each point on a surface, which are equal to the inverse of the respective radii of two circles

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7/13 tangential to the surface in two perpendicular directions. In this way, a curvature is defined by a positive number, and the resulting concavity can be oriented on one side of the surface or on the other. Hereinafter, the term "average curvature of the face S1" is understood to mean an average value of all the curvatures thus defined at all points on the face S1. This average curvature is indicated in abbreviated form as the curvature of the S1 face. In the context of the invention, this curvature can correspond to the values used in ophthalmic, in particular to correct various ametropias. For example, the average curvature of face S1 can be equal to 6 diopters, however the invention can be applied when face S1 has a higher curvature.

[0021] As shown in figure 2a, a continuous film 2 is covered with a layer of adhesive on one of its faces. The faces of film 2 can be parallel. The face containing layer 3 is referenced S2 and is intended to be turned towards lens 1 when film 2 is applied against the face S2 of lens 1. For this reason, it is called the application face. This face of film 2 on the opposite side of face S2 is referred to as S3 and is called the outer face, in relation to its position in the final assembly of film 2 with lens 1. Film 2 can have a thickness e2 that is between 10 and 500, one (microns), for example equal to approximately 75 pm, and layer 3 can have a thickness and ₃ which is between 10 and 100 pm, for example equal to approximately 25 pm. The film 2 and layer 3 are preferably transparent. Film 2 can be based on polyethylene terephthalate or PET, cellulose triacetate or CTA, polyvinyl alcohol or PVA, a polyimide, polyethylene naphthalate or PEN, or polycarbonate. Film 2 may also have a structure based on several overlapping layers adhering to each other.

[0022] The adhesive layer 3 can be laid on the application face S2 of the film 2 before the last one is applied against the lens 1. Alternatively, the film 2 can be placed on the face S1 of the lens 1, or both on the faces S1 and S2 of lens 1 as in film 2 respectively, depending on the nature of the adhesive used. This adhesive may comprise a pressure sensitive adhesive or PSA, or a heat curable or UV curable adhesive. In particular, this can be a PSA based

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8/13 acrylic or silicone based. Such adhesives are considered to be known to you, and their description and use will not be discussed further here. Alternatively, the layer 3 adhesive may also comprise a latex or a polyurethane. It can be deposited on film 2 using one of the known methods, among which can be mentioned spin coating, dip coating, shoveling, etc.

[0023] Film 2 may itself have an optical effect. This is the case in particular for a polarizing film, a dyed film, a color-enhancing film, a filter-forming film or a photochromic film.

[0024] Film 2 can also serve as a support for one or more functional coatings that can be arranged on the outer face S3. Such coatings may be intended to provide the optical element with additional functionalities, such as, for example, an anti-reflective function, an anti-dirt function, an anti-scratch function, a hydrophobic function or a combination thereof. As an example, the film 2 of figure 2b has, on its face S3, a layer structure 4 comprising an anti-reflective coating 4a, an anti-scratch coating 4b and a hydrophobic coating 4c.

[0025] Film 2 may also include a set of cells 20 that are juxtaposed parallel to one side of the film. Neighboring cells of this set are separated by walls 21 substantially perpendicular to the face of the film. Each cell 20 forms a cavity that is capable of containing a substance introduced into it. Cells 20 can be placed in a regular or irregular manner next to each other. In particular, they can form a hexagonal lattice. In figure 2c, film 2 is in a state ready to be attached to lens 1, while cells 20 are still empty. Alternatively, figure 2d shows a film 2 containing cells, in which cells 20 were filled in advance with a substance and then hermetically sealed by an additional film 5. Film 5 is attached to the tops of walls 21. In this case, film 2 it is fitted with lens 1, while the substance has already been introduced into cells 20. The substance contained in cells 20 may, in a non-limiting manner, have a variable optical refractive index,

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9/13 especially an index that can be subsequently adjusted by irradiation. This can also be a photochromic substance, an active substance based on liquid crystals, an electrochromic substance, etc. Such films are described, in particular, in patent application WO 2006/013250.

[0026] A device that is particularly adapted to implement an adhesion method, according to the invention, will now be described. This device requires a particularly small number of operations to manipulate film 2 and lens 1. In addition, its use is quick and simple, and the set obtained has an optical quality compatible with an ophthalmic application.

[0027] As shown in figure 3, a chamber 10, for example of cylindrical shape and vertical geometric axis, is opened in its upper face. A side wall 10a of the chamber 10 is provided at its upper end with a system for fixing a film to seal the chamber 10. This fixing system may include a sealing device, for example, an O-ring seal intended for be compressed between the side wall 10a and a peripheral edge of the film by a fixing ring 11, using fixing screws (not shown).

[0028] A lens holder 12 is placed in chamber 10 at the end of a cylinder 13. The cylinder 13 is combined with a piston 14 in order to allow the holder 12 to rise inside the chamber 10, beyond the level of the ring. fixing 11. The displacement of the support 12, by means of cylinder 13 and piston 14, is controlled from outside the chamber 10 using, for example, an electrical or hydraulic control device. Such a remote control device is considered to be known and will not be further described here.

[0029] Chamber 10 is provided with an orifice 15 which is connected via an appropriate conduit to an external gas source (not shown). This source makes it possible to establish a controlled pneumatic pressure inside the chamber 10. Thus, the inside of the chamber 10 can be at a higher pressure or a lower pressure in relation to the ambient pressure that exists outside the chamber 10. The pressure in the chamber 10 can be varied and controlled independently of the position and displacement of the support 12. In other words, the pressure in chamber 10 and the

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10/13 support position 12 are adjusted by separate controls.

[0030] Finally, a heating system 16 is placed above the chamber 10, facing the closing film of the chamber. An infrared radiation heating system allows particularly simple and quick use, but as an alternative, other heating systems can be used.

[0031] Advantageously, the heating system 160, the pressure inside the chamber 10 and the position of the piston 14 are controlled by a programmable controller that performs a sequence of variations of the various parameters of the device to effect adhesion, according to the invention.

[0032] Lens 1 is installed on bracket 12 with the S1 side facing up. The support 12 is then placed in a low position inside the chamber 10. The film 2 is fixed in the chamber 10 by means of the ring 11, with the face S2 containing the adhesive layer 3 facing towards the inside of the chamber. In this configuration, the S1 face of lens 1 is some distance below the S2 face of film 2, and chamber 10 is hermetically sealed by film 2.

[0033] A first method of operation will now be described, which is suitable when the S1 surface of lens 1 is convex.

[0034] During a first stage, the pressure inside chamber 10 is increased in order to create a pneumatic pressure difference ΔΡ1 between the two sides of the film, whose pressure difference is between 10000 Pa (0.1 bar) and 400000 Pa (4.0 bar), preferably between 10,000 Pa (0.1 bar) and 100,000 Pa (1.0 bar). The pressure outside chamber 10 is atmospheric pressure and chamber 10 is pressurized. During this stage, the film 2 is heated using the system 16, to make it more flexible and more extensible. The temperature T1 of film 2 is then between 80 ° C and 180 ° C. Optionally, it may be advantageous to heat film 2 before increasing the pressure in chamber 10, and to continue heating in order to maintain the temperature of film 2 while the pressure in chamber 10 is being increased. The film 2 then adopts an approximately spherical shape as it is inflated towards the outside of the chamber 10, as illustrated in figure 4a.

[0035] The heating of the film is then stopped and the temperature of film 2 is

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11/13 returned to a value approximately equal to the ambient temperature To, between 10 ° C and 40 ° C. During a second stage, the pressure inside the chamber 10 is reduced in order to obtain a pneumatic pressure difference AP2 between the two sides of the film 2 which is between 5000 Pa (0.05 bar) and 30000 Pa (0.3 bar) . The chamber 10 is thereby kept continuously pressurized. Due to the particularly elastic behavior of film 2, the filling of film 2 towards the outside of chamber 10 decreases. The AP ₂ overpressure is selected so that the curvature of the film 2 becomes slightly less than the curvature of the convex face S1 of lens 1 (figure 4b). These first and second steps constitute the pre-formation of film 2 in an intermediate curvature between the initially zero curvature of film 2 and the curvature of the S1 face of lens 1.

[0036] During a third stage, the piston 13 is raised so that the S1 side of the lens 1 contacts the adhesive layer 3 that is present on the S2 side of the film 2. Due to the respective curvatures of the two sides S1 and S2, contact first occurs at the center of lens 1 (figure 4c) and then extends radially as piston 13 continues to lift. The S1 face of lens 1 therefore pushes the film 2 towards the outside of the chamber 10, in addition to the position of the film before the piston 13 starts to rise. The face S1 of the lens 1 is thus progressively pressed against the face S2 of the film 2, with a relative rate of movement that can be between 0.1 and 1.0 mm / s. An upper limit value for this speed depends on the plastic behavior of film 2. Thus, film 2 adopts the shape of face S2 without forming a crease or tear (figure 4d). During this third stage, the temperature of the film is constant, remaining for example equal to the ambient temperature.

[0037] Lens 1 can be kept pressed against film 2 for a retention time that can be between 0.5 seconds and 2 minutes. The overpressure in chamber 10 is then removed, cylinder 13 is lowered again, and retaining ring 11 is removed. The lens 1 is then recovered, with the film 2 adhered to the face S1. When layer 3 consists of a curable adhesive, lens 1 and film 2 are exposed to UV radiation or heat flux in order to permanently fix the adhesion.

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Optionally, this exposure step can be performed before lens 1 and film 2 are removed from chamber 10, while overpressure AP ₂ is still applied.

[0038] Lens 1 can then be trimmed. During this operation, peripheral parts of lens 1 and film 2 are simultaneously removed, and an eyeglass lens is obtained in which film 2 and the S1 face of lens 1 have identical dimensions. [0039] A second method of operation can be implemented based on the configuration corresponding to figure 4a. Film 2 is then substantially cooled down to room temperature T0, but the overpressure in chamber 10 is now adjusted so that film 2 adopts a curvature substantially identical to that of the S1 face of lens 1 (figure 5a). The overpressure inside chamber 10, indicated by AP2 ·, can again be between 5000 Pa (0.05 bar) and 30000 Pa (0.3 bar), but it is slightly above the AP ₂ value of the first operating method, all other things being identical.

[0040] During an additional step illustrated by figure 5b, the interior of the chamber 10 is under reduced pressure compared to the exterior of the chamber, which remains at atmospheric pressure. The curvature of film 2 is then inverted and film 2 expands towards the interior of chamber 10. The face S2 of film 2 is then convex. During this third stage, the difference in pneumatic pressure applied between the two sides of film 2, indicated by AP3, can be between 5000 Pa (0.05 bar) and 50000 Pa (0.5 bar) in absolute value, corresponding to a pressure reduction obtained by suction through orifice 15.

[0041] Piston 13 is raised while film 2 remains at temperature T0 and the pressure difference is maintained at AP ₃ . The S1 and S2 faces of lens 1 and film 2 come into contact, respectively, in the central zone of lens 1 (figure 5c). The contact zone between lens 1 and film 2, through layer 3, then extends radially as the piston 13 rises. The S1 face of lens 1 then pushes film 2 towards the outside of chamber 10. When the S1 face of lens 1 is convex, the S2 face of film 2 becomes concave again while face S1 is progressively pressed against face S2 . Film 2 thus recovers the direction of curvature

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13/13 initially acquired during the first stage of the method, illustrated in figure 5a. Figure 5d shows the configuration of film 2 when the contact zone between lens 1 and film 2 has not yet reached the entire face S1. The curvature of film 2 is reversed at the limit of the contact zone between the film and the lens, while that contact zone continues to increase radially. The movement speed of cylinder 13 can again be between 0.1 and 1.0 mm / s.

[0042] Figure 5e corresponds to the end of the elevation of the cylinder 13 when the lens 1 is pressed against the film 2 on the entire face S1. The second method of operation can then be continued in the same way as the first method of operation.

[0043] It should be understood that the numerical values indicated above in the detailed description of the invention, according to two different methods of implementation, were given merely as an illustration. In particular, the temperature and pressure difference values have to be adapted when the curvature of the S1 face of lens 1 varies. Similarly, they must be adapted when the material and / or the thickness of the film 2 varies, according to the thermomechanical properties of that material.

[0044] It should also be indicated that the second method of operation described can be used when the S1 face of lens 1 is concave. In this case, the sub-pressure AP3 is advantageously suitable for the film 2 to adopt an inverse curvature, which is slightly larger than that of the S1 face of lens 1. Finally, it must also be understood that the invention can be implemented for substrates other than one ophthalmic lens. In particular, it can be used to attach a film to a measuring instrument lens or an optical viewfinder lens, to mask glass, window glass, etc.

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Claims (24)

1. Method for adhering a film (2) having a flat initial shape to a curved face of a substrate (1), the method being characterized by comprising the following steps: a) when the film is at a temperature above 40 ° C, a peripheral edge of the film (2) is held firmly and a pneumatic pressure difference is applied between two sides of the film until an application face (S2) of the film become curved with a greater curvature than an average curvature of the face (S1) of the substrate; b) when the temperature of the film has dropped below 40 ° C, the difference in pneumatic pressure applied between the two sides of the film is adjusted so that the curvature of the application face (S2) of the film becomes equal to or less than that the curvature of the face (S1) of the substrate; and c) while maintaining the pneumatic pressure difference set in step b), the face (S1) of the substrate is pressed against the application face (S2) of the film until a complete contact is established between the film and the face of the substrate, a layer of an adhesive (3) being placed between the film (2) and the substrate (1). 2. Method according to claim 1, characterized by the fact that step a) is carried out while simultaneously heating the film (2), and step (b) is carried out when the temperature of the film is equal to the ambient temperature. 3. Method, according to claim 1 or 2, characterized by the fact that the temperature of the film during step a) is between 80 ° C and 180 ° C. 4. Method according to any one of the preceding claims, characterized by the fact that the difference in pneumatic pressure applied in step a) between the two sides of the film is between 10,000 Pa (0.1 bar) and 400000 Pa (4, 0 bar). 5. Method, according to claim 4, characterized by the fact that the difference in pneumatic pressure applied in step a) between the two sides of the film is between 10000 Pa (0.1 bar) and 100000 Pa (1.0 bar) ). 6. Method according to any of the preceding claims, Petition 870170073850, of 9/29/2017, p. 24/29 2/5 characterized by the fact that in step c), the face (S1) of the substrate is pressed against the application face (S2) of the film with a relative movement rate between 0.1 and 1.0 mm / s. Method according to any one of claims 1 to 6, characterized in that the face (S1) of the substrate is convex and in which: in step a) the difference in pneumatic pressure is applied between the two sides of the film so that the application face (S2) of the film becomes concave with a greater curvature than the curvature of the face (S1) of the substrate; and in step b), the difference in pneumatic pressure applied between the two sides of the film is reduced so that the application face (S2) of the film remains concave and the curvature of the application face becomes less than the curvature of the face (S1) of the substrate. 8. Method according to claim 7, characterized by the fact that the difference in pneumatic pressure applied between the two sides of the film after step b) is between 5000 Pa (0.05 bar) and 30000 Pa (0.3 Pub). Method according to any one of claims 1 to 6, characterized in that in step a), the difference in pneumatic pressure is applied between the two sides of the film so that the application face (S2) of the film it becomes concave with a greater curvature than the curvature of the face (S1) of the substrate and where step b) then comprises the following two substeps: b1) when the temperature of the film has dropped below 40 ° C, the difference in pneumatic pressure applied between the two sides of the film is reduced so that the application face (S2) of the film remains concave and the curvature of the application face becomes equal to the curvature of the face (S1) of the substrate; and then b2) the pneumatic pressure difference is modified by inverting the pressure difference signal between the two sides of the film so that the application face (S2) of the film becomes convex. 10. Method according to claim 9, characterized by the fact that the face (S1) of the substrate is convex and in which the application face (S2) of the film becomes concave again when the face of the substrate is progressively Petition 870170073850, of 9/29/2017, p. 25/29 3/5 pressed against the film application face in step c). 11. Method according to claim 9 or 10, characterized by the fact that the difference in pneumatic pressure applied between the two sides of the film after step b1) is between 5000 Pa (0.05 bar) and 30000 Pa (0 , 3 bar). 12. Method according to any one of claims 9 to 11, characterized in that the difference in pneumatic pressure applied between the two sides of the film after step b2) is between 5000 Pa (0.05 bar) and 50000 Pa (0.5 bar) in absolute value. 13. Method according to any one of the preceding claims, characterized by the fact that, after step c), the substrate 1) is kept pressed against the film (2) for a time between 0.5 seconds and 2 minutes. 14. Method according to any one of the preceding claims, characterized in that the adhesive layer (3) is disposed on the application face (S2) of the film before step c). Method according to any one of the preceding claims, characterized in that the adhesive layer (3) comprises a pressure-sensitive adhesive or a heat-curable or UV-curable adhesive. 16. Method according to any one of the preceding claims, characterized in that the substrate (1) comprises an optical lens. 17. Method according to claim 16, characterized by the fact that the substrate (1) comprises an ophthalmic lens. 18. Method according to any one of the preceding claims, characterized in that the film (2) comprises a material based on polyethylene terephthalate, cellulose triacetate, polyvinyl alcohol, a polyimide, polyethylene naphthalate or polycarbonate. 19. Method according to any one of the preceding claims, characterized in that the film (2) includes a functional coating (4) on an external face (S3) of the opposite film from the application face (S2). 20. Method according to claim 19, characterized in that the functional coating (4) comprises an anti-reflective coating, a Petition 870170073850, of 9/29/2017, p. 26/29 4/5 anti-dirt coating, anti-scratch coating, hydrophobic coating or a combination of some of the coatings. 21. Method according to any one of the preceding claims, characterized by the fact that the film (2) includes a set of cells (20) juxtaposed parallel to one side of the film, neighboring cells of the set being separated by walls (21) perpendicular to the film face. 22. Method according to any one of the preceding claims, characterized by the fact that steps a) to c) are performed using a device that comprises: - a sealed chamber (10) provided with a system (11) for fixing the peripheral edge of the film (1) in order to hermetically seal the chamber with the film; - a device (16) for heating the film attached to the chamber and a device for controlling the temperature of the film attached to the chamber; - a device (15) for varying the pneumatic pressure inside the chamber and a device for controlling the pneumatic pressure in relation to the pressure outside the chamber; - a substrate support (12) placed in the chamber; and - devices (13, 14) for moving the substrate support inside the chamber, which are designed to press the substrate against the film, in which steps a) and b) are performed by activating the device (15) to vary and control the pressure pneumatics inside the chamber and step c) is performed by activating the device to move the substrate support (13, 14). 23. Device for carrying out the method as defined in any one of claims 1 to 22, characterized in that it comprises: a sealed chamber (10) provided with a system (11) for fixing a peripheral edge of a film in order to hermetically seal the chamber with the film; a device (16) for heating the film when attached to the camera; a device (15) for varying a pneumatic pressure inside the chamber and a device for controlling the pneumatic pressure in relation to a pressure outside the chamber; Petition 870170073850, of 9/29/2017, p. 27/29 5/5 a substrate support (12) placed in the chamber; and devices (13, 14) for moving the substrate support within the chamber, which are designed to press the substrate against the film. 24. Device according to claim 23, characterized in that it additionally includes an automatic control system designed to control the device (15) for varying and controlling the pneumatic pressure inside the chamber, the device for varying and controlling the heating of the film and the devices (13, 14) for moving the substrate support. Petition 870170073850, of 9/29/2017, p. 28/29 1/3